Heavy load indicator for watt-hour meters



July 20, 1943.

H. M. WITHER OW HEAVY LOAD INDICATOR FOR WATTHOUR METERS Filed Nov. 4,. 1940 3 Sheets-Sheet 1 inventor-z Harry M. Witiwjrow, b w

His Attorney.

July 20, 1943.

PERCENT REGISTER TIM H. M. WITHEROW HEAVY LOAD INDICATOR FOR WATTHOUKMETERS Filed Nov. 4, '1940' 3 Sheets-Sheet 2 I00 200 300 PE RCE/VT LOAD CURRENT Inventor-z Hard-9 M. Wither-ow,

His ttorney.

July 20, 1943. H. M. WITHEROW ,895

' 1mm LOAD INDICATOR FOR WATTHOUR METERS File d Nov. 4; 1940 a Sheets-Sheet a Inventor 2 Harry M. Witherow,

l'lis ttor-ney.

I invention as'appIi'e'd-to an ifitegxating meterfei Patented July 20, 1943 r HEAVY m tpplicafioa met-be 4, 19 50 at, :ieigs iaf may wiaimbmtdn, Ema," assi iii General. Qompany, fiacccrpo r atipi qf -Myin'vention relates to'an attachment for'eee tric' meters ofthe'integrating type, such for e9!- ample as watthour meters an d other'inetets' oftfie watthour type; such 1 as r'eactive c'cmpciint hour a '01 volt ampere hear mete s, for registering-heavy a I load conditions." For example, 'my' i attachment may registetfthewatthwi's usd'when 'thid'ad current) exceeds: a predeter'rriinedaiiibuntiarid V- alsc 'the'fr x aximiim 'watthoiii-s ueed at bi" above x the. predeterminedload 'ciirgent" '0 er any com m tinuous period of time. nieasa r ement indications thus obtained are in the nature of z mandmeasurements and: may he used as such fer billing purpasesi The mm'sii'reinents areaic I useful for determining a custolr iers nieter 'cr' I5 wiringis adequate forthecharacter'of lead which" he draws from theiiline. Thyin fcrmatiehfob tainedi tram such -measurements: is alse helpful V in determining if acustomers jmte is preper an'd whether or not, theinstatlation of a bldck ixitervat '20 I v i me and t0 provide-ambient temperature-come pensation', lemploy-a tOggIe'spring-atfl made '0;

demandmeterisjustified.. Although the measurement's ebtained by-"my' attachment,arewatthour'measuremeiitsgvoltam pere' hour measurements or reactive vbit ampei e hour. measurements; depending cmthekind cifayZi meter the i attachment is used on; the iiie'asme mentspare taken in response "tupredetermined in the claimsfappexided hei etb. For a better understanding of my invention reference is made ta the following drawings'in. which Figs; 1 and represent slightly difie 'enfi' embediments 0f the watthour, type for jtetaiizi sig wattho-i gs simied when the lead camps excessjcfa predetermined amdunti an a nger ierits of Figs. laiid'in additioii diice a 'i'i'ndicatidnicf the maximum measare rriexit ,ef the integrating meter during any one 'cciifii'iiioii'sfperiu-d"efex 'cess load current. vFig. 3" isa load curreritfegi- 4 is 'aL -pIa-n 'view of the mag'neticWIfeI-Qf Fig.5;

mined amount.

@Reierri'ng nqw to-Fig. 1;l'haveshcwflportions pf a watthour meter ccr iprisin'g' the induction mgr: Hi; the Voltage" magnet n, umnenia' net ll; shaft II, and the usual register gearirig' hav ing pointers conn'pted'to be driven fiom the shaftl i through ,reductibn geazingat FE and IG and-a shaft IE 'Ifhpo V ers'of this register sooperate with stationary"dialwlllrin the regi'ster faceplate-"21 0n shaft? it is a' ivhee f [8 which 7 at lr'times mayl'drive awheeIf. l"9 and its ahaftufl I The-wheels i tand w gre shiftedinto: aridoiit f of mesh in fespengto thefetid currentby a; bimetallic thermal strip 3} havingoneendfixed r and the end ceupl'ed tb lever 25 by-thb-rod 32; The iheatd by a heater resi$tame l3 invs e'r 'with'ttie -current coil o'fthe meter. Asqssr p-fltfsheatedgit bends dciwliwai'd' ass-shown to msliwtieels l wands amf h caot it's free endaymoves npwsird' to "'demesh these wheels. TFO" make" theseactions quick" and posi- Bi'metal trrerppos the movement caused byfstfip '3! ii in dir'e'ctims until 'asubstantial force ,Hambexr built up to cause aisnap action pring-34 also bends in response to'ambien -temperatm'e' changes in adirection am} tothe' Tex 'tent'iiece'ssary to: cdmpensatcstrip 3ifcrsuchz I changee and caus'ef the action to be independent 'of ambierit temperature changes; 7 [The shaft which is; driven tl irough g'ears 'l's-"ar d I 9 when in amazing reiatimi winds up a-suitable-spririg 'on weight represented at-f35"and aiso; advances a" .do'g ifi at "itsi forward end. is normally" biasedhy'the" spriI-ig 35, against-a "step 3]; but} when advanced shovesa i'ricticn pointer up;

Ward over a: scare as; ,wnen'me gea rs lama-5 is are demeshe'd; spring 35 retains the deg"- 38 cmin' M ter-ciockwiseg-againstrxstop '31 but thefffrictiorr I I pointer 3R remain: at: the indication tometerreade'r oncea rriqrith orat suehetiier netei" reading periods as seem desirable; This .part if the mechanism" is somewhat similar to; knewii maximum demand mters'exeept that the period predetem ii edfvaliie fqr whichthe cl'utch cprat ing mechanism is adjusted. When'geais' IE and" ing predetermined heavy load current.

curve B, Fig. 3;

l9 are disengaged, gear I 9 is engaged with a gear 46 on a shaft 4| which drives a dial or dials 42 for registering the total watthours consumed dur- The driving power for register v42 is the spring 35 or equivalent in which energy is stored from the 'watthour meter. It is seen that because of the snap action of the gear shift, gear 19 meshes with gear 46 at substantially the same'instant that it is demeshed from gear l8 so that the forward measurement advancements of gear 19 are completely transferred to and .accumulated on reg'-- ister 42.

registration.

Overshooting of such registration 'is prevented because stop 3lprevents anyover- It will be noted that by this arrangement the" i 1 watthour meter is required to provide the energy that is stored in spring 35. "If the register parts I Y are made light and delicate and are carefullyadjusted so as to permit the use of a light spring at35, this may not seriously influence the accuracy of the watthour meter. ,However, I may compensate for this extra load on the watthour meter and-at the sametime increase its ,useful.

overload range in a desirable manner. a Fig. 3 shows load accuracy curve. Atypical of induction watthour metersvcompensated for. cur

rent flux damping onoverload'in accordance with United States LettersPatent 1,727,509, Septembar-l0, 1929. It is apparent that an additional load on such a meter such as might be causedby engaging gears l8 and-l9 of applicants Fig. lat 200% load currentor at some. greater load current would tend toincrease the error in registration. Additional overload compensation for the meter is therefore desirable both for the reason explained inthe above mentioned patent and because of the tendency to addloadwhen my invention as arranged in Fig. 1 is employed.

Accordingly, I may employ the bimetallic motor means 3lfor theadditional purpose of stepping up the calibration of thejmeter when the load current reaches the :point where gears ,l6 and H! are engaged. One way of accomplishing this resultis shown in Fig. l wherethe rod 32 has an extension 43 for'operatinga mercury switch 44 arranged to open resistance circuit 45 in shunt to the current coil ofthe meter when gears! and 19 are engaged. The resistance circuit 45 is so adjusted in comparison with the resistance of the current coil that when'the shunt circuit is closed, the meter calibration conforms to curve A, Fig. 3. At the predetermined load current this shunt circuit'is openedas shown in Fig. 1. This increases the torque. Calibration with any load added by reason of the engaging of 1 gears l8 and I9 now conforms to the dotted line It is. at onceapparent that this expedient greatly improves the. registration accuracy of the .meter over the overload range which is indicated to be between.200 and 300% load current in Fig. 3.

I may also make use of thesame mercury: switch 44 to shift the shunt circuit in parallel.

change in calibration of the meter is adjusted by.

the resistance at 45 and the adjustment of the heater characteristics is made "by the position along the heater 33 at which the shunt circuit is tapped thereto.

In Fig. 4 I have shown a'further modification of the invention so arranged as to be added to existing meters without disturbing the customary register andwith a separate drive to the heavy current responsive attachmenn, In this arrangement the register 2| and the maximum demand d0g'36 are driven from a shaft 46 arranged to be driven from the meter disk It] through a magnetic induction drive receiving its flux from a small permanent magnet 48. This drive merely consists of two serrated dish-shaped members 41 .of magnetic material secured to the opposite poles -01 the axial permanent magnet 48 so as to form a magnetic wheel: having opposite polarity parts which embrace the edge of the disk armature l0. A-plan viewof this wheel is shown in Fig. 5. If the magnetic wheel is held stationary as is the case at low and normal load currents on the meter, itserves to supply a small but constant damping flux and hence a small part of the meter damping,.the greater part of which is supplied by thev usual damping magnet shown at 49. In adding this attachment to an existing meter, the damping suppliedby the magnet 43 will be .reduced by the small amount of damping contributed by-wheeL 4] when held stationary. The usual-adjustment for moving magnet ,49 towards the shaft I3will1suflice for such recalibration.

, A-bimetallic strip'49' heated by the load current heater 50 is provided for operating a brake finger 5| and a gear shift 52. Mild snap action of the thermostat betweenits two positions is provided byatoggle spring 53.

1 In the position of the parts shownyit is assumed that the meter current is normal and the strip .49 in approximately a normal position with the brake finger 5| holding wheel 41 from rotation and with the gear-52 betweenshaft46 and the demand attachment demeshed. Under these conditions a smallweight54 will have returned the dog-36 to zero positiona'gain'st its stop. When a predetermined heavy load current occurs for any length oftime,; the strip 49" flexes upward to remove the brake finger 5| allowing shaft 46 to be driven and at the same time. engaging gear 52 completing the drive to the. demand attachment. The demand attachment operates in the usual way to register the maximum rotation of shaft 46. during any one continuous heavy load current cycle. Register 2|, permanently geared to shaft 46, registers the total rotations of shaft 46.. It is evident that-the load on shaft 46 is constant so that the registrations will be proportional to the speed of rotation of armature Ill.

The release of brake 5| permitting wheel 41 to rotate reduces the drag orfdamping produced by wheel 41, since now the relative movement between these parts and hence the damping is reduced. Only enough damping now exists todrive the shaft 46. Hence, we have a beneficial heavy load current compensating condition that will lift the meter registration curve on overload current in a. manner depicted by thedotted line curve B of Fig. 3, although this compensation is obtained in a different manner as compared t0 F g. .1.

An adjustable resistance in shunt to heater will be noted that in Fig. 4 the strip 49' when.

2,324,895 j r j Y 3 I An integrating meter of the watthour type,

heated,v flexes away from the heater resistance illand this feature may be'emphasized to the extent necessary to cause the reverse operations of the strip to occur atsubstantially the same load current. r f t H The arrangement shown in Fig. 2 is generally similar to that of Fig. 1 "with the exception of the overcurrent registration feature. In Fig. 2 this feature is intendedprimarilyyto indicate that the watthour' has exceeded a predetermined amount during some overload current period and does not necessarily show the maximum watthour registration during such overload current periods. In Fig. .2 when the loadcurrent exceeds a predetermined'amount thegear 64 is thrown into mesh with gear 18 as indicated. Dog

'36 is then advanced to movefdemand pointer 38.

. a registerrdriven by said meter for registering thetotal,integrationthereof, a second register means, meansire'sponsive to the increase and decrease of the load current of said meter above and below substantially a predetermined value for respectively connecting and disengaging said second register meansto and fromdriving rela-i tion with said meter and means also operated 'by said current responsive means for modifying the calibration of said meter in a manner to improve its accuracy.

up scale 39 so long as the overload continues or 7 until the blank sector 65 of gear 64 comes opposite gear l8. which occurs when the demand. pointer ,38 has been advanced to theupper end? of the scale. Then if the overload current still persists, slipping occurs between gears Y6 and I8 until the current drops and'thegears 'aresepa-.

rated and dog 36 is returned to the zero .'stop'31 by spring 35.

By this arrangement relatively low overload demands can be measured and indicated with good accuracy. Also; the apparatus for which the deviceis intended. This form of the invention is particularly useful for survey work to'determine, for example, if a customers load is such as to warrant installinga block interval demand meter. :The'o'verload accuracy compensating feature of Fig. 1 may of course be used withthe modification shown in'Fig. 2 and rent to line current when the thermal device.

3| operates. t

In accordance with the provisions of the patent statutes, I have described the principle of opera}:

tion of my invention together with the apparatus which I now consider to represent the best. em-

bodiment thereof, but I desire to have it understood that the apparatus shown is only illustra- 'tive and that the invention may be carried out by other means. o

What I claim as new and desire to secure by Letters Patent of theUnitedStates is:

i is protected from damage andblocking of register I40. in case the demand exceeds the range trolling operations occur., l r I 3. An integrating meter of the watthour type,- 'a demand device, a dog for advancing said de- .2. An integrating meter of thewatthour type,

a, register continuously connected to be driven by said meter, a second register means, a driving connection between said second register means v and meter which may be rendered active or inactive, means responsive to the load current of saidmeterfor controlling said driving connec-. tion so that the secondregister means is driven by the meter only when the meter load'currentor exceeds 'a' predetermined value and means for correctively' adjusting the calibration of saidmeter when such load 'current' responsive conpviceya drive including a pair of gearsbetween said meter and dog which may be disengaged,

said drive causing the advance of said dog when the meter is in operation and thedrive is en-' gaged, means for retractingsaid dog when said drive is disengagedyand means responsive to j the load currentof said meter for engaging said drive when the load current of the meter exceeds. apredetermined'value and for disengaging said drive when the load current is belowsuch value, one of said gears containing a blank portion in its toothed portion to prevent the advance of said dog beyonda given point. p

4. In an integrating meter of the watthour type, a maximum demand indicator, a shaft. for I operating said indicator and means responsive to the increase and decrease of the load current of said meter above and ,below approximately a predeterminedvalue for respectively connecting and disengaging said shaft to and from driving relation with said meter, and means for resetting said shaft whereby said demand indicator'indicates the maximum integration of said meter over the one period of greatest overload during which the load current has exceeded such 3 predetermined value between the resetting oper- .ations of said shaft. Y

HARRY-.M. WITVHEROW. 

